Gamma linolenic acid regulates expression of maspin and the motility of cancer cells

A meta‑ and bioinformatics analysis of maspin expression levels influencing the prognosis of patients with breast cancer

Maspin is a serine protease inhibitor that is encoded by the human SERPINB5 gene. As a tumor inhibitor, it can inhibit the growth of tumor cells, increase adhesion between tumor cells and inhibit tumor angiogenesis. In the present study, a meta- and bioinformatics analysis was performed through the PubMed and China National Knowledge Infrastructure databases including entries added until up to March 20, 2023. It was found that compared with normal breast tissue, maspin expression was downregulated in breast cancer tissue. Maspin expression was negatively associated with lymph node metastasis. According to Kaplan-Meier plotter, it was found that lower maspin expression was negatively associated with the overall and distant metastasis-free survival rate of patients with estrogen receptor-positive, luminal A and grade 2 breast cancer. High expression of maspin was also positively associated with the relapse-free survival rate of patients of the luminal A subtype. Low maspin expression was positively associated with the post-progression and distant metastasis-free survival rate of the progesterone receptor-negative subtype. According to the GEPIA database, SERPINB5 mRNA expression was higher in normal than breast cancer tissues and negatively correlated with the TNM stage. High expression of maspin was also positively associated with the overall survival rate. In the UALCAN database, it was found that the mRNA and promoter methylation levels of SERPINB5 were higher in normal than in breast cancer tissues. These findings suggest that the expression of maspin may serve as a potential marker to indicate the occurrence, subsequent progression and even prognosis of breast cancer.

Zinc oxide nanoparticles enhance expression of maspin in human breast cancer cells

Toxic and apoptotic impacts of zinc oxide nanoparticle (ZNP) on different cancer cells have been reported. Maspin (a mammary serine protease inhibitor) as a tumor suppressor gene can inhibit tumor growth and metastasis. The expression of maspin is modulated by p53, Bcl-2 family genes, and estrogen receptor α (ER-α). This study aimed to assess the ZNP effects on maspin expression in MCF-7 cells (a breast cancer cell). Experimental groups (ZNP5, ZNP10, and ZNP20) received 5, 10, and 20 μM/mL ZNP for 48 h, respectively. 17-β-estradiol (E2) was used to evaluate the role of ER-α in the anticancer impact of ZNP. Cell viability, Annexin V, migration assay, gene expression, and western blotting methods were applied to evaluate ZNP effects on the MCF-7 cells. ZNP at the concentrations of 10 and 20 μM/mL could significantly decrease the viability and migration rate, and significantly increase apoptosis percentage in the MCF-7 cells. ZNP significantly enhanced mRNA expression and protein level of maspin in MCF-7 cells in a concentration-dependent way. ZNP concentration-dependently elevated mRNA expression and protein level of p53 and Bax while reduced the expression of Bcl-2 and ER-α. E2 promoted cancer cell growth by enhancing survival and migration rates. E2 treatment reduced mRNA expression and protein level of maspin and p53, and elevated Bcl-2 expression. ZNP considerably changed these events induced by E2 in the MCF-7 cells. It is concluded that the maspin overexpression is one of the toxic mechanisms of the ZNP on the ER-α-positive breast cancer cells, and can suppress the migration of these cells.

Maspin: molecular mechanisms and therapeutic implications

Maspin, a non-inhibitory member of the serine protease inhibitor superfamily, has been characterized as a tumor suppressor gene in multiple cancer types. Among the established anti-tumor effects of Maspin are the inhibition of cancer cell invasion, attachment to extracellular matrices, increased sensitivity to apoptosis, and inhibition of angiogenesis. However, while significant experimental data support the role of Maspin as a tumor suppressor, clinical data regarding the prognostic implications of Maspin expression have led to conflicting results. This highlights the need for a better understanding of the context dependencies of Maspin in normal biology and how these are perturbed in the context of cancer. In this review, we outline the regulation and roles of Maspin in normal and developmental biology while discussing novel evidence and emerging theories related to its functions in cancer. We provide insight into the immense therapeutic potential of Maspin and the challenges related to its successful clinical translation.

Are the olive oil and other dietary lipids related to cancer? Experimental evidence

There is a wealth of evidence supporting the relationship between dietary lipids and cancer, particularly those of the breast, colon and rectum and prostate. The main support comes from the international correlational studies and, especially, from experimental ones. The evidence from human analytical studies is less consistent because of several conflicting findings, probably due to methodological issues. Experimentally, it has been clearly demonstrated that quantity and type of dietary lipids as well as the particular critical phases of the carcinogenesis in which they act, are the essential factors in this relationship. Thus, whereas high dietary intake of n-6 polyunsaturated fatty acids (PUFA), primarily LA, and saturated fat has tumor-enhancing effects, long chain n-3 PUFA, CLA and GLA have inhibitory effects. Monounsaturated fatty acids (MUFA), mainly OA, present in high quantities in olive oil, seem to be protective although some inconsistent results have been reported. Bioactive compounds of virgin olive oil may also account for the protective effect of this oil, which is the main source of fat in the Mediterranean diet. Experimental studies have also provided evidence of several putative mechanisms of action of dietary lipids on cancer. Lipids can influence the hormonal status, modify cell membranes structure and function, cell signalling transduction pathways and gene expression, and modulate the function of the immune system. Although further studies are needed to evaluate and verify these mechanisms in humans, based on the multiple ways dietary lipids can act, they may have an important influence on tumorigenesis.

Maspin and Mutant p53 expression in malignant melanoma and carcinoma: use of tissue microarray

Maspin (mammary serine protease inhibitor), a member of the serpin family, has been shown to inhibit angiogenesis, tumor invasion, and metastasis. Previous studies suggest a p53-dependent regulatory pathway of maspin protein expression. Its loss correlates with progression of disease in both breast and prostate cancer. We studied the in vivo correlation of maspin expression with p53 mutation in malignant melanoma (MM) with and without use of tissue microarray (TMA). Seventy-seven MMs were immunostained on individual slides for maspin and p53 expression. Results were validated in 1 slide for each marker on a TMA system (TARP-2) with 498 tissue cores (0.6-mm diameter) from MM, other tumors, and normal tissue. The relationship between maspin and p53 in MM and carcinomas of other sites (breast, ovary, colon, lung, and prostate) was delineated using Pearson chi analysis. The inverse relationship between maspin and p53 expression predicted by hypothesized p53 regulation of maspin transcription, or any other correlation between these 2 markers, is not demonstrated in MM cases, using either classic individual slide (P=0.20) or TMA (P=0.85) methods when cutoffs for both markers are set at 10% or greater of cells staining. Even when cutoffs are altered with respect to either intensity or percentage of cells staining, no relationship is demonstrated between these markers, with either TMA or the conventional slide method. TMA immunostaining also showed no such relationship in carcinomas of the various other sites sampled-including breast and prostate, where previous studies have suggested a linkage. Despite published experimental evidence linking these 2 markers, this study failed to demonstrate correlation between maspin loss and p53 expression in MM using both individual slides and TMA, or in TMA of other carcinomas. Use of TMA is a quick, easy, and inexpensive method of immunohistochemical analysis of large numbers of cases, both to validate results obtained from individual slides and to assess specificity in a variety of neoplasms. However, heterogeneity and minimal tumor may lead to variable results.

Molecular mechanisms of the effects of olive oil and other dietary lipids on cancer

Cancer is one of the main causes of mortality worldwide. Geographical differences in incidence rates suggest a key effect of environmental factors, especially diet, in its aetiology. Epidemiologic and experimental studies have found a role of dietary lipids in cancer, particularly breast, colorectal, and prostate cancers. Their incidence in the Mediterranean countries, where the main source of fat is olive oil, is lower than in other areas of the world. Human studies about the effects of dietary lipids are little conclusive, probably due to methodological issues. On the other hand, experimental data have clearly demonstrated that the influence of dietary fats on cancer depends on the quantity and the type of lipids. Whereas a high intake of n-6 PUFA and saturated fat has tumor-enhancing effects, n-3 PUFA, conjugated linoleic acid and gamma-linolenic acid have inhibitory effects. Data regarding MUFA have not always been conclusive, but high olive oil diets seem to have protective effects. Such effects can be due to oleic acid, the main MUFA in olive oil, and to certain minor compounds such as squalene and phenolic compounds. This work aims to review the current knowledge about the relationship between dietary lipids and cancer, with a special emphasis on olive oil, and the molecular mechanisms underlying these effects: modifications on the carcinogenesis stages, hormonal status, cell membrane structure and function, signal transduction pathways, gene expression, and immune system.

Gum mastic increases maspin expression in prostate cancer cells

AIM

To study whether gum mastic, a natural resin, can regulate maspin expression in prostate cancer cells, and further investigate the mechanisms involved in this regulatory system.

METHODS

RT-PCR and Western blotting were used to detect maspin expression at the transcriptional and translational levels. Reporter gene assay was used to investigate the effect of gum mastic on the maspin promoter. The binding activity of negative androgen-responsive element (ARE) and positive Sp1 element in the maspin promoter were studied by electrophoretic mobility shift assay.

RESULTS

Gum mastic induced maspin mRNA and protein expression, and the maspin promoter activity was enhanced with gum mastic treatment. Finally, gum mastic inhibited the ARE binding activity and increased the Sp1 binding activity in the maspin promoter.

CONCLUSION

Gum mastic enhances maspin promoter activity by suppressing ARE binding activity and enhancing Sp1 binding activity, and the increased activity in the maspin promoter finally leads to the up-regulation of both its mRNA and protein levels.

Epigenetic regulation of maspin expression in the human placenta

Maspin, a tumour suppressor gene, is differentially expressed in the human placenta. Decreased expression of maspin in the first trimester corresponds with the period of maximum trophoblast invasion, suggesting a role in cell invasion and motility. Although methylation of CpG islands regulates maspin expression in cancer cells, the mechanism of maspin regulation in the human placenta is unknown. Our objectives were to determine the role of epigenetic alterations in the regulation of maspin expression in the placenta. Placental samples obtained from 7 to 40 weeks' gestation were used for bisulphite sequencing and chromatin immunoprecipitation (ChIP) PCR. There was no significant change in the methylation indices in the promoter region of maspin throughout gestation. The levels of histone modifications associated with transcriptionally active chromatin were significantly different in placental tissues from second and third trimester relative to those from first trimester. Addition of trichostatin A (TSA) to placental explants increased the maspin mRNA expression (8- to 20-fold), whereas addition of 5-aza-cytidine (5-AzaC) had no effect on maspin expression. Our data suggest that maspin expression in the human placenta is regulated by changes in histone tail modifications. This is the first report of selective histone modifications associated with differential placental gene expression in human gestation.

Epigenetic regulation of maspin expression in human ovarian carcinoma cells

OBJECTIVE

Maspin expression is often deregulated in human cancer cells compared to their normal cells due to loss of epigenetic control. In contrast to normal human ovarian surface epithelial (HOSE) cells, ovarian carcinoma cells display a gain of maspin mRNA expression. The objective of this study was to determine whether gain of maspin expression in ovarian cancer is governed by epigenetic mechanisms.

METHODS

We examined the cytosine methylation and chromatin accessibility status of the maspin promoter in normal HOSE cells and ovarian carcinoma cells with real-time RT-PCR, sodium bisulfite genomic sequencing, and chromatin accessibility assays. 5-Aza-2'-deoxycytidine (5-aza-dC) was used to induce demethylation of the maspin promoter. Ad p53 was used to induce transient overexpression of wild-type p53.

RESULTS

Normal HOSE cells were maspin-negative in association with methylation of the maspin promoter. In the maspin-positive ovarian cancer cell lines, the maspin promoter was unmethylated. Increased maspin expression in ovarian carcinoma cells was accompanied by a more accessible chromatin structure in the maspin promoter. In the maspin-negative ovarian cancer cell line A222, maspin could be induced following 5-aza-dC treatment or by forced overexpression of p53.

CONCLUSIONS

These results suggest that changes in cytosine methylation and chromatin accessibility play an important role in maspin expression in human ovarian carcinoma. Deregulation of maspin expression in ovarian cancer is due to loss of epigenetic control as has been shown in other cancers. This observation provides further evidence of the strict epigenetic control of the maspin gene.

Protective role of glucose-6-phosphate dehydrogenase activity in the metabolic response of C6 rat glioma cells to polyunsaturated fatty acid exposure

Polyunsaturated fatty acids (PUFAs) can influence tumor growth and migration, both in vitro and in vivo. The PUFA gamma-linolenic acid (GLA) has been reported to improve the poor prognosis associated with human gliomas, although its effects at sublethal concentrations on residual cells postsurgery are poorly understood. The study investigated the effects sublethal PUFA doses (90 or 150 microM) may have on rat C6 glioma cell energy metabolism, since an adequate energy supply is essential for cell proliferation, migration, and apoptosis. Of note was the identification of mitochondrial heterogeneity in relation to the mitochondrial membrane potential (MMP), which has been suggested but unproven in previous studies. GLA and eicosapentaenoic acid (EPA) caused significant changes in cellular fatty acid composition and increased the percentage of cells with a low MMP after a 96-h exposure period. The presence of PUFAs inhibited C6 cell proliferation and migration, although apoptosis was not induced. The protein expression and activity of glucose-6-phosphate dehydrogenase was increased after 96-h incubation with 90 microM GLA and EPA and would allow redox regulation through increased NADPH production, permitting the maintenance of adequate intracellular reduced glutathione concentrations and limiting rates of lipid peroxidation and reactive oxygen species generation. Neither NADP(+)-isocitrate dehydrogenase nor NADP(+)-malate dehydrogenase activity responded to PUFAs, suggesting it is glucose-6-phosphate dehydrogenase that is the principal source of NADPH in C6 cells. These data compliment studies showing that higher concentrations of GLA induced glioma cell death and tumor regression and suggest that GLA treatment could be useful for the inhibition of residual cell proliferation and migration after surgical removal of the tumor mass.

Prognostic value of maspin mRNA expression in ER alpha-positive postmenopausal breast carcinomas

Maspin, a member of the serpin family, has a role in cell migration, angiogenesis and apoptosis. Little is known of the clinical significance of maspin gene expression in human cancers. We developed a real-time quantitative RT-PCR assay to quantify the full range of maspin mRNA copy numbers in a series of 10 ER alpha-positive and 10 ER alpha-negative breast tumours. We observed a statistical link between low maspin mRNA levels and positive oestrogen status (P=0.0012). In consequence, to better assess the prognostic value of maspin gene expression in breast cancer, we then quantified maspin mRNA content in an additional independent well-defined cohort of 105 ER alpha-positive postmenopausal breast cancer patients treated with primary surgery followed by adjuvant tamoxifen alone. Maspin expression varied widely in tumour tissues (by nearly four orders of magnitude), being underexpressed in 33 out of 105 tumours (31.4%) and overexpressed in 24 out of 105 tumours (22.9%) relative to normal breast tissues. Immunohistochemical studies demonstrated that maspin protein was strictly expressed in myoepithelial cells of normal breast tissue and in tumour epithelial cells, exclusively in maspin-overexpressing tumours. Patients with tumours overexpressing the maspin gene had significantly shorter relapse-free survival after surgery than patients whose tumours normally expressed or underexpressed maspin (P=0.0011). The prognostic significance of maspin overexpression persisted in Cox multivariate regression analysis (P=0.0024). These findings show that the maspin mRNA level can have important prognostic significance in human breast cancer, and point to the maspin gene as a putative molecular predictor of hormone responsiveness in breast cancer.

Maspin functions as tumor suppressor by increasing cell adhesion to extracellular matrix in prostate tumor cells

PURPOSE

Maspin, a unique member of the serine protease inhibitor family, shows tumor suppressing activity for breast cancer progression and metastasis. Few studies have directly linked maspin function to prostate cancer. We used prostate tumor cells derived from the TRAMP (transgenic adenocarcinoma of mouse prostate) prostate tumor model to study the tumor suppressive function of maspin in prostate cancer.

MATERIALS AND METHODS

Maspin cDNA was introduced via a retroviral plasmid into TRAMP C2N prostate tumor cells, which are aggressive and invasive in nature. We investigated the tumorigenesis of these stable cell lines in vitro by assessing the growth rate, anchorage independence and adhesion to extracellular matrix proteins such as fibronectin and laminin.

RESULTS

Stable cell lines expressing maspin had decreased tumorigenic potential, as assessed by anchorage independent growth in soft agar assay compared with controls. Maspin stable transfectants showed decreased metastatic potential, as evaluated by modified Boyden chamber assay and increased adhesion to fibronectin and laminin.

CONCLUSIONS

Our study confirms that maspin has a tumor suppressive role not only in breast cancer, but also in prostate cancer. The data in this study suggest that maspin can decrease the tumorigenic and metastatic potential of prostate tumors, most probably by remodeling cell-extracellular matrix interactions or triggering extracellular matrix mediated signaling pathways that negatively regulate tumor migration and invasion.

5 alpha-reductase-catalyzed conversion of testosterone to dihydrotestosterone is increased in prostatic adenocarcinoma cells: suppression by 15-lipoxygenase metabolites of gamma-linolenic and eicosapentaenoic acids

Although the androgens, testosterone (T) and its highly active metabolite dihydrotestosterone (DHT) play a role in the development and progression of prostate cancer, the mechanism(s) are unclear. Furthermore, 5 alpha-reductase which catalyze the conversion of T to DHT, has been a target of manipulation in the treatment of prostatic cancer, hence synthetic 5 alpha-reductase activity inhibitors have shown therapeutic promise. To demonstrate that nutrients derived from dietary sources can exert similar therapeutic promise, this study was designed using benign hyperplastic cells (BHC) and malignant tumorigenic cells (MTC) derived from Lobund-Wistar (L-W) rat model of prostatic adenocarcinoma to test the effects of gamma-linolenic acid (GLA), eicosapentaenoic acid (EPA) and their 15-lipoxygenase metabolites on cellular 5 alpha-reductase activity. Our data revealed: (i) that incubation of MTC with [3H]-T resulted in marked conversion to [3H]-DHT when compared to similar incubation with BHC; (ii) that DHT-enhanced activity of 5 alpha-reductase was inhibited 80% by 15S-hydroxyeicosatrienoic acid, the 15-lipoxygenase metabolite of GLA, when compared to 55% by 15S-hydroxyeicosapentaenoic acid, the 15-lipoxygenase metabolite of EPA; and (iii) that their precursor fatty acids, respectively, exerted moderate inhibition. Taken together, the study underscores the biological importance of 15-lipoxygenase metabolites of polyunsaturated fatty acids (PUFAs) in androgen metabolism.

Modifications in mitochondrial metabolism and ultrastructure and their relationship to tumour growth inhibition by gamma-linolenic acid

Walker 256 tumour-bearing rats were fed pelleted chow containing low-gamma-linolenic acid (GLA) (2.98%) or high-GLA (5.55%) during the twelve-day period after subcutaneous implantation of the tumour. The presence of n-6, polyunsaturated GLA in the diet caused a concentration-dependent decrease in tumour growth, reaching an almost 50% reduction in final tumour weight in the high-GLA group. The eicosatrienoic acid content of the whole tumour homogenate and of the Percoll-purified mitochondrial fraction was increased by the GLA-rich diets. Changes in the fatty acid composition of the cytoplasmic acyl CoA pool were also found, with increases in GLA content in both the low- and high-GLA groups. Additionally, increases in eicosatrienoic acid and arachidonic acid were found in the high-GLA group. Both the cytoplasmic acyl CoA content and the mitochondrial acyl CoA synthetase activity were increased by GLA in the diet and lipid peroxidation was also increased as determined by an increase in TBARS content. Changes in mitochondrial fatty acid composition were accompanied by a decrease in the mitochondrial membrane potential in the high-GLA group. Tumours from the control and GLA groups were examined by transmission electron microscopy. This revealed an increase in mitochondrial area and volume in the high-GLA group, in comparison with the control group, as well as a change in general cell ultrastructure, with many cells found in an apoptotic state or in a necrotic state, possibly secondary to apoptosis. The data presented show that the addition of GLA to the diet of Walker 256 tumour-bearing rats can greatly decrease the rate of development of the tumour burden. This may be, in part, due to the accumulation of poorly metabolised acyl CoA's within the tumour cell cytoplasm which, when coupled with altered mitochondrial composition, membrane potential and ultrastructure, may be a signal for cell death.

Inhibition of aflatoxin B1 genotoxicity in human liver-derived HepG2 cells by kolaviron biflavonoids and molecular mechanisms of action

Kolaviron biflavonoids have demonstrated antihepatotoxic activity in animal studies. The present study investigated the possible chemopreventive potential of kolaviron in inhibiting aflatoxin B1 (AFB1) genotoxicity in HepG2 cells. Kolaviron inhibition of AFB1-induced cytotoxicity by clonogenic assay and genotoxicity by [3H]thymidine incorporation in unscheduled DNA synthesis were evaluated, including antioxidant potential of kolaviron determined by its reduction in the intracellular reactive oxygen species level induced by hydrogen peroxide. Induction of AFB1-detoxicating enzymes such as cytochrome P450 3A4 (3A4) and glutathione S-transferases (GSTs) A1-1/ A2-2 (alpha) and M1B (mu) was determined by reverse transcription polymerase chain reaction (RT-PCR) and northern blotting for the messages and western immunoblot analysis for protein. Kolaviron significantly (P < 0.01) and dose-dependently inhibited the cytotoxicity (by 71.6%) and genotoxicity (47.1%) of AFB1 in HepG2 cells. The antioxidant potential of kolaviron compared favourably with values for the standard antioxidant trolox C (53.8% at only 4.5 x 10(-2)-fold kolaviron concentration) but was below that of butylated hydroxyanisole (58.1% at a ninefold kolaviron concentration). It induced about threefold increases in the messages for 3A4 and GSTs alpha and mu, including a twofold increase in GSTalpha protein. Kolaviron may have chemopreventive potential in inhibition of human AFB1 genotoxicity and possibly hepatocarcinogenesis.

p53 regulates the expression of the tumor suppressor gene maspin

Maspin has been shown to inhibit tumor cell invasion and metastasis in breast tumor cells. Maspin expression was detected in normal breast and prostate epithelial cells, whereas tumor cells exhibited reduced or no expression. However, the regulatory mechanism of maspin expression remains unknown. We report here a rapid and robust induction of maspin expression in prostate cancer cells (LNCaP, DU145, and PC3) and breast tumor cells (MCF7) following wild type p53 expression from an adenovirus p53 expression vector (AdWTp53). p53 activates the maspin promoter by binding directly to the p53 consensus-binding site present in the maspin promoter. DNA-damaging agents and cytotoxic drugs induced endogenous maspin expression in cells containing the wild type p53. Maspin expression was refractory to the DNA-damaging agents in cells containing mutant p53. These results, combined with recent studies of the tumor metastasis suppressor gene KAI1 and plasminogen activator inhibitor 1 (PAI1), define a new category of molecular targets of p53 that have the potential to negatively regulate tumor invasion and/or metastasis.

Peroxisome proliferator activated receptor-gamma (PPAR-gamma) mediates the action of gamma linolenic acid in breast cancer cells

Gamma linolenic acid (GLA) is a polyunsaturated fatty acid, which induces cytotoxicity and regulates cell adhesion in cancer cells. The molecular mechanism of these actions is not clear. We have shown that GLA acts via peroxisome proliferator activated receptors (PPARs), by stimulating their phosphorylation and translocation to the nucleus. Removing PPAR gamma with antisense oligos abolished the effect of GLA on the expression of adhesion molecules and tumour suppressor genes, whereas removal of PPAR alpha had no effect. Tissues from patients with breast cancer showed a reduction of expression of both PPARs in cancer tissues, as compared with normal. Thus, PPAR gamma serves as the receptor for GLA in the regulation of gene expression in breast cancer cells.

Tumor invasion: role of growth factor-induced cell motility

Cancer progression to the invasive and metastatic stage represents the most formidable barrier to successful treatment. To develop rational therapies, we must determine the molecular bases of these transitions. Cell motility is one of the defining characteristics of invasive tumors, enabling tumors to migrate into adjacent tissues or transmigrate limiting basement membranes and extracellular matrices. Invasive tumor cells have been demonstrated to present dysregulated cell motility in response to extracellular signals from growth factors and cytokines. Recent findings suggest that this growth factor receptor-mediated motility is one of the most common aberrations in tumor cells leading to invasiveness and represents a cellular behavior distinct from-adhesion-related haptokinetic and haptotactic migration. This review focuses on the emerging understanding of the biochemical and biophysical foundations of growth factor-induced cell motility and tumor cell invasiveness, and the implications for development of targeted agents, with particular emphasis on signaling from the epidermal growth factor (EGF) and hepatocyte growth factor (HGF) receptors, as these have most often been associated with tumor invasion. The nascent models highlight the roles of various intracellular signaling pathways including phospholipase C-gamma (PLC gamma), phosphatidylinositol (PI)3'-kinase, mitogen-activated protein (MAP) kinase, and actin cytoskeleton-related events. Development of novel agents against tumor invasion will require not only a detailed appreciation of the biochemical regulatory elements of motility but also a paradigm shift in our approach to and assessment of cancer therapy.

Concentration- and time-dependent effects of gamma-linolenic acid supplementation to tumor cells in culture

Gamma-linolenic acid (GLA) supplemented to neuroblastoma SK-N-BE, tubal carcinoma TG and colon carcinoma SW-620 cells was incorporated into phospholipids in all the cell lines (although to different extents), in a concentration- and time-dependent manner. All the cell lines were able to metabolize GLA to arachidonic acid, SK-N-BE being the most active. Supplementation with low GLA concentrations for short periods was not sufficient to impair cell proliferation; only higher amounts of GLA had an anti-proliferative effect also in short times. In these conditions, the antiproliferative effect of GLA is probably due to cellular dysfunction caused by fatty acid modifications.

Importance of dietary gamma-linolenic acid in human health and nutrition

Considerable debate remains regarding the distinct biological activities of individual polyunsaturated fatty acids (PUFA). One of the most interesting yet controversial dietary approaches has been the possible prophylactic role of dietary gamma-linolenic acid (GLA) in treating various chronic disease states. This strategy is based on the ability of diet to modify cellular lipid composition and eicosanoid (cyclooxygenase and lipoxygenase) biosynthesis. Recent studies demonstrate that dietary GLA increases the content of its elongase product, dihomo-gamma-linolenic acid (DGLA), within cell membranes without concomitant changes in arachidonic acid (AA). Subsequently, upon stimulation, DGLA can be converted by inflammatory cells to 15-(S)-hydroxy-8,11,13-eicosatrienoic acid and prostaglandin E1. This is noteworthy because these compounds possess both anti-inflammatory and antiproliferative properties. Although an optimal feeding regimen to maximize the potential benefits of dietary GLA has not yet been determined, it is the purpose of this review to summarize the most recent research that has focused on objectively and reproducibly determining the mechanism(s) by which GLA may ameliorate health problems.

Regulation of tight junction permeability and occludin expression by polyunsaturated fatty acids

Tight junctions (TJ) are the topical most structure in epithelial and endothelial cells and play a key role in the control of permeability and prevention of tumour cell invasion of endothelium. In this study we examined the effects of a range of polyunsaturated fatty acids on the function of TJs and the expression of occludin, a key molecule in the TJs of the human vascular endothelial cell line, ECV304. Treatment of the endothelial cells with gamma linolenic acid, an anti-cancer PUFA, increased the transendothelial cell resistance (TER) and reduced the paracellular permeability to large molecules. The effects were seen without any changes in the viability of the endothelial cells. Occludin, a recently identified molecule, which plays a major role in tight junctions was up-regulated by this fatty acid as revealed by both Western blotting and immunofluorescence. Other fatty acids were also tested. Eicosapentaenoic acid (EPA) also exerted an up-regulatory effect, but LA and AA down-regulated the expression. We conclude that GLA and EPA which also have other anti-cancer effects, regulate the expression of occludin in endothelial cells and thus contribute to the modification of the TER of these cells.